An actuator has been hitherto used as a means for transporting a workpiece. The actuator basically comprises a rotary driving source arranged at the inside of a housing of the actuator, a driving force-transmitting means such as a ball screw for converting the rotary driving force of the rotary driving source into rectilinear motion to be transmitted to another member, and a slider for making displacement along the longitudinal direction of the actuator by the aid of the driving force-transmitting means.
The slider makes displacement along an opening of the housing, and it transmits the rotary motion of the rotary driving source disposed in the housing to the outside of the housing as the rectilinear motion.
However, the conventional actuator involves the following fear depending on the environment in which the actuator is used. That is, for example, dust, water, water vapor, coolant, cutting fluid, and grinding fluid make invasion through the opening of the housing, and they adhere to the driving force-transmitting means. When the actuator is driven, the dust or the like is caught in the gap between the driving force-transmitting means and the slider, resulting in stop or breakage of the actuator. Further, the following problem is pointed out. That is, when the actuator is used at a place to be prevented from dust or the like, such as those relevant to the medical field, those relevant to the field of food, and clean rooms, any leakage occurs from the actuator to the outside, concerning, for example, the dust and the grease used for the motor, the ball screw, the bearing and the like for constructing the driving force-transmitting means and the rotary driving source.
This invention has been made in order to solve the problems described above, an object of which is to provide an actuator which makes it possible to avoid adhesion of dust or the like to a driving force-transmitting means, wipe out the fear of stop or breakage or the like of the driving force-transmitting means, and avoid leakage of dust or the like to the outside.